|Tom Hartnett, Comrex. Technical Director. ‘I feel strongly that it’s time to leverage the benefits of IP codecs into the station’s on-air phone system.’
Radio World asked
several codec suppliers about trends in their area of expertise and we got back
some great information. This is one in a series.
How have codecs
changed in recent years?
Hartnett: Besides the general
movement from ISDN to IP, codecs have certainly made inroads in providing solid
performance over “average-quality” wired IP links.
Most good modern codecs have dynamic buffer managers
and other tools to compensate for the “raw” nature of the public Internet. We
hear of very few operational issues these days, beyond initial setup, from
wired IP users.
On the wireless end, seamless integration with things
like 4G and Wi-Fi is hot. Also codec manufacturers now deploy compatible modes
so they can talk to each other. And finally, several manufacturers have
introduced lower-cost, simpler devices that bring the benefits of IP codecs to
a larger user base.
direction is codec design heading?
Hartnett: The industry hasn’t
seen a mass migration to laptop-based codecs, although they exist. We’ve been
concentrating on providing easy interface to existing smartphone apps as
companions our hardware codecs, as there is a definite segment of user who is
excited about that. But there are limits to smartphone codecs — like form
factor, wireless-only operation and lack of stereo — and there are many users
(e.g., voiceover, sportscasting, studio-studio, backup STL) for which they’ll
never make sense.
I feel strongly that it’s time to leverage the
benefits of IP codecs into the station’s on-air phone system. We’ve introduced
an IP-based multi-line call in system that does all the old-fashioned telephone
integration, but can also take calls from codec users (and wideband smartphone
apps) and blends them seamlessly into the same conference.
leery of relying on the Internet for mission-critical audio transport?
Hartnett: Engineers just need to be smart
about where they are applying these tools. Most smart customers know not to
show up to a ballgame with 30,000 smartphone users and expect good results on
3G. And not to buy a $35/month consumer-grade DSL as your STL backbone.
Of course there’s a lot of different kinds of users,
and sometimes projects are green-lighted only because they can be done cheaply.
I find those the most interesting and fun, but in most cases those types of
projects can survive some rocky performance.
But as far as real pros with budgets and reliability
needs, they can be met with smart design and planning, and installation of
wired Internet whenever possible.
This is an important point: Wireless services can be a
nice shortcut for quick-shots and reporters, but will never rival the
reliability of wired. And mission-critical wired IP requires QoS arrangements
and Service Level Agreements. In the early days, it was pretty common for users
to try IP coding, have a failure and announce the technology “not ready.”
There’s too much cost-savings at stake to ignore IP codecs anymore.
What is the
“state of the art” in bitrates and algorithms?
Hartnett: For pro-grade studio-studio and
STL, it’s often cost-effective to go linear, or with a lossless codec like
FLAC. This will require a reasonably “fat” IP pipe, but is often doable these
days at reasonable cost, and removes any concerns about codec cascading.
Short of that, a relatively high-bitrate (at least 256
kbps) AAC coding works well. For budget broadcasters this can be lowered, and
HE-AAC can be utilized below 100 kbps and sound quite good.
The premiere “remote broadcast” coding algorithm is
definitely AAC-ELD, which can provide good-sounding mono with low delay at 48
kbps, and stereo below 100 kbps. This means the same algorithm can be deployed
on wired links, Wi-Fi and 3G/4G without much regard to how “fat” the network
is. We used to believe algorithms that work down in the sub-20 kbps range
offered an edge. We find this is less so these days — networks seem much more
binary in their performance (i.e., either working, or if faulty, blocking all
What about HD
Voice and other developments on the network provider side?
Hartnett: For general users, HD Voice has an
“Achilles heel,” which is its inability to work if the standard public
telephone network is involved. But since service providers are willing to
deploy it (I suspect mostly for marketing impact), it could be a real boon for
Our industry has the high-quality contribution
application covered with existing products, but we still often take
horrible-sounding calls on-air. How many meticulously engineered stations air
hours of cellphone audio per day from listeners? It drives me crazy. It
prompted us to design a product specifically to integrate HD Voice and Skype
calls to the studio. We even provide a simple HD Voice app you can provide to
guests and listeners.
Beyond that, the wide deployment of 4G LTE creates an
environment where odds of success for IP wireless remotes are enhanced
What is the next
big challenge facing codec designers?
Hartnett: Video! Radio
stations are becoming multi-platform content providers, and video is often a
part of that change. There used to be a big distinction between video and audio
content producers, and that’s now all blurred.
What is your
newest or most notable product?
Hartnett: There are two:
STAC-VIP, a VoIP studio telephone system that integrates HD Voice calls, Skype,
and “normal” callers; and our LiveShot codec that delivers high-quality video
on poor networks with very low delay with the right set of controls and
functions for broadcast, because video isn’t just for TV anymore.